oMEGACat. V. Helium Enrichment in ω Centauri as a Function of Metallicity

Author(s): C. Clontz, Anil C. Seth, Z. Wang, S. O. Souza, M. Häberle, M. S. Nitschai, N. Neumayer, M. Latour, A. P. Milone, A. Feldmeier-Krause, N. Kacharov, M. Libralato, A. Bellini, G. van de Ven, M. Alfaro-Cuello
Abstract: Constraining the helium enhancement in stars is critical for understanding the formation mechanisms of multiple populations in star clusters. However, measuring helium variations for many stars within a cluster remains observationally challenging. We use Hubble Space Telescope photometry combined with MUSE spectroscopic data for over 7200 red giant branch stars in ωCen to measure helium differences between distinct groups of stars as a function of metallicity, separating the impact of helium enhancements from other abundance variations on the pseudo-color (chromosome) diagram. Our results show that stars at all metallicities have subpopulations with significant helium enhancement (ΔY_min ≳ 0.11). We find a rapid increase in helium enhancement across low metallicities ([Fe/H] ≃ −2.05 to [Fe/H] ≃ −1.92), with this enhancement leveling out at ΔY = 0.15 at higher metallicities. The fraction of helium-enhanced stars steadily increases with metallicity from 10% at [Fe/H] ≃ −2.04 to over 90% at [Fe/H] ≃ −1.04. From these measurements, we calculate the total mass in helium produced over the cluster’s lifetime, finding M He tot ∼ 2.7 × 1 0 5 M ⊙ . This study is the first to examine helium enhancement across the full range of metallicities in ωCen, providing new insight into its formation history and additional constraints on enrichment mechanisms.
Organisation(s): Department of Astrophysics
External organisation(s): University of Utah, Max-Planck-Institut für Astronomie, Georg-August-Universität Göttingen, University of Padova, Osservatorio Astronomico, Leibniz-Institut für Astrophysik Potsdam, Space Telescope Science Institute, Universidad Central de Chile
Journal: Astrophysical Journal
Volume: 984
No. of pages: 15
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/adc1c5
Publication date: 05-2025
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/41fdd618-c372-4080-8682-735d7ac36fec

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